P2Y2 receptor agonist with enhanced stability protects the heart from ischemic damage in vitro and in vivo

Extracellular nucleotides acting via P2 receptors play important roles in cardiovascular physiology/pathophysiology. Pyrimidine nucleotides activate four G protein-coupled P2Y receptors (P2YRs): P2Y(2) and P2Y(4) (UTP-activated), P2Y(6), and P2Y(14). Previously, we showed that uridine 5'-triphosphate (UTP) activating P2Y(2)R reduced infarct size and improved mouse heart function after myocardial infarct (MI). Here, we examined the cardioprotective role of P2Y(2)R in vitro and in vivo following MI using uridine-5'-tetraphosphate delta-phenyl ester tetrasodium salt (MRS2768), a selective and more stable P2Y(2)R agonist. Cultured rat cardiomyocytes pretreated with MRS2768 displayed protection from hypoxia [as revealed by lactate dehydrogenase (LDH) release and propidium iodide (PI) binding], which was reduced by P2Y(2)R antagonist, AR-C118925 (5-((5-(2,8-dimethyl-5H-dibenzo[a,d][7]annulen-5-yl)-2-oxo-4-thioxo-3,4-dihydropyrimidin-1(2H)-yl)methyl)-N-(1H-tetrazol-5-yl)furan-2-carboxamide). In vivo, echocardiography and infarct size staining of triphenyltetrazolium chloride (TTC) in 3 groups of mice 24 h post-MI: sham, MI, and MI+MRS2768 indicated protection. Fractional shortening (FS) was higher in MRS2768-treated mice than in MI alone (40.0 +/- 3.1 % vs. 33.4 +/- 2.7 %, p<0.001). Troponin T and tumor necrosis factor-alpha (TNF-alpha) measurements demonstrated that MRS2768 pretreatment reduced myocardial damage (p<0.05) and c-Jun phosphorylation increased. Thus, P2Y(2)R activation protects cardiomyocytes from hypoxia in vitro and reduces post-ischemic myocardial damage in vivo.